PSI - Issue 45

Oscar Zi Shao Ong et al. / Procedia Structural Integrity 45 (2023) 140–147 O.Z.S. Ong et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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mass imperfection

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Fig. 1. Simply supported FG CNT reinforced plate with mass imperfection.

To study the effects of thickness of the plate on the fundamental out-of-plane natural frequency of a perfect (no mass imperfections) FG CNT reinforced square plate, with UD CNT distribution, and different CNT volume fractions, / b h is varied in a range of 10 to 50 and a = 1 m. The dimensional (to help demonstrate the real world effects) fundamental natural frequency (rad/s) is plotted in Fig. 2. It is first noted that as the CNT volume fraction increases, the natural frequency increases. As the plate thickness increases, regardless of whether CNT reinforced or non-CNT reinforced, the natural frequency increases and the rate of increase increases too as the thickness increases, with the CNT reinforced plates showing a higher sensitivity to the change of thickness.

Fig. 2. Fundamental natural frequencies of a simply supported UD CNT reinforced square plate, with b / h = 10 – 100.

To help further study the effects of plate dimensions on the natural frequency, varying the aspect ratio, / b a in a range of 0.25 to 4 ( b is varied in a range of 1 to 4 while simultaneously a is varied in a range of 4 to 1), while maintaining 0.02m h  and 0kg M  , the dimensional fundamental natural frequency (rad/s) of a UD CNT reinforced plate is plotted in Fig. 3. The logarithmic scale is applied in the x axis. For a non-CNT reinforced plate, the lowest natural frequency is noted when the plate has a square shape   / 1 b a  . As the aspect ratio increases/decreases from 1 (i.e. rectangular shape), the natural frequency increases. As expected, the natural frequency is symmetrical about aspect ratio of 1. However, this does not hold true after CNT reinforcements are introduced, due to the anisotropic properties of CNT. The natural frequency increases, alongside the rate of increase increases, as the width of the CNT reinforced plate increases beyond the square plate. However, as the width decreases from aspect ratio of 1, the natural frequency decreases at the start and eventually increases. A higher aspect ratio also resulted in higher natural frequency for the CNT reinforced plates when compared with the non-reinforced case.